Hepatic CT enhancement. Part II. Alterations in contrast material volume and rate of injection within the same patients.

Abstract

To evaluate the effects of alterations in contrast material volume and injection rate on liver computed tomographic (CT) enhancement within the same patients. Forty patients underwent repeat CT within 6 months, one with 150 mL of nonionic contrast material at 2 mL/sec, the other with 150 mL (n = 8, group A), 100 mL (n = 14, group B), or 180 mL (n = 18, group C) at 3 mL/sec. Comparisons were made only within the same patients. In group A, mean liver enhancement was greater with the higher rate (3 mL/sec) up to 130 seconds after injection, mean peak liver enhancement was greater by 10 HU, and mean time to peak enhancement was shorter by 15 seconds. In group B, mean peak enhancement was greater with 150 mL by 9 HU, and mean time to peak enhancement was longer by 27 seconds. In group C, peak enhancement and time to peak liver enhancement were greater. Contrast material volume and injection rate have interdependent effects on liver enhancement and potentially tumor conspicuity. Higher rates compensate partially for lower volume, but enhancement is still reduced. The optimal window of time for imaging after injection varies with injection technique.